Folding wall assembly



'Dec. 23, 1969 1.. s. TURNER ET AL 3,

FOLDING WALL ASSEMBLY 4 Sheets-Sheet 1 Filed May 18, 1967 m r N 6 6 N R w 6%. MMM j wwm 3. rflr la TH NM 9- V W i M LW w. W M W A a??? 3 6 7 Q MW i W W a m V m 8 L 6 m K M v u w w 7 9A 7 M 7 l M W W 6 2 m o aw i H 3 A lllllllll M- \8 N 4 2 Q a 4 a M7/2M7a fig I ATTORNEYS Deb. 23, 1969 Filed May 18, 1967 L. B. TURNER ET AL FOLD ING WALL AS SEMBLY 4 Sheets-Sheet 2 1.. BOWMAN TURNER W/LL MM M. HARMO/V INVENTORS JMZ/MMWMW ATTORNEYS ec. 23, 1969 1.. B. TURNER ET 3,485,234

FOLDING WALL ASSEMBLY 4 Sheets-Sheet 3 Filed May 18, 1967 IN VENTORS L. BOWMAN TURNER WILL/AM M. HARMOA/ MWMMf/MMW ATTORNEYS Dec. 23, 1969 TURNER ET AL 3,485,284

FOLDING WALL ASSEMBLY Filed May 18, 1967 4 Sheets-Sheet 4 IN VENTORS L. BOWMAN TURNER W/LL/AM M. HARMO/V ATTORNEYS United States Patent 3,485,284 FOLDING WALL ASSEMBLY Lloyd Bowman Turner, t'lolumbus, and Wiliiani M. Harmon, Worthington, Ohio, assignors to United Sheet Metal (10., inc, Columbus, Ohio, a corporation of Ohio Filed May 18, 1967, Ser. No. 639,468 Int. Cl. EtlSf /20; Etifib 9/06 lU.S. Cl. 1601 12 Claims ABSTRACT OF THE DISCLOSURE Several embodiments of sheet material folding wall assemblies, especially for horizontally and vertically disposed automatic fire dampers, the Wall being made from sheet metal strips with large and small spiral form roll hinge elements on respective opposite longitudinal edges of the strips. Large and small hinge roll elements on adjacent strips slide into mated interlocked hinging engagement to make a zig-zag folding wall. A rectangular frame, made from formed side and end members or as a duct section from fiat sheet metal confines the folding wall and includes preformed or channel strip guide tracks which cooperate with end lug projections of the hinge roll elements of each strip to guide the wall as it folds and unfolds. A fusible link on bracket clips holds the wall in folded condition. The horizontally disposed damper includes coiled, flat spring power units to unfold the wall. The spiral form hinge roll edges are based on a mathematical Archimedean spiral curve, the smaller hinge roll being formed with its spiral form laying adjacent the inside of the mathematical curve and the larger hinge roll being formed with its spiral form laying adjacent the outside of the mathematical curve.

RELATED APPLICATION The present invention is an improvement over the invention disclosed in a co-pending US. application for Letters Patent Ser. No. 566,361, filed on July 19, 1966 by R. Vassaux for Fire Damper.

BACKGROUND OF THE INVENTION This invention relates to folding wall or shutter assemblies and more particularly relates to such assemblies made as automatic folding fire walls or dampers for use in ducts, conduits or passages through building fire walls wherein the folding walls are made of strips which fold and unfold in zigzag or accordian arrangement.

Fire walls made from a plurality of strips, blades or slats are known in the prior art and they have been of several types, sliding, rolling and folding. The latter two types utilize a hinging connection between adjacent strips, the rolling type of wall requiring a lesser range of hinging action between strips than do the folding walls, and hence in the area of rolling walls a problem of providing an inexpensive hinge structure capable of hinging through a substantial arc of swing has not been present as it has in folding wall construction. When the strips are made from sheet metal, the prior art teaches the roll forming of slidably interlocked edges of such strips. Many such roll edge shapes have been proposed, e.g., roll edges with cross-sections having the general shape of spirals, circles, combinations of spirals and circles, and combina tions of circular arcs and straight transitions, but various problems are presented by previous known roll hinges. Many are virtually impossible to form in production quantities, and this is particularly troublesome when one considers the small hinge dimensions desired for duct type fire dampers. Others have complex roll shapes and require multiple expensive rolling operations. Other shapes are too large and prevent the desirable aspect of compact stacking when the strips are folded. Other shapes,

3,485,284 Patented Dec. 23, 1969 while easy to make and permitting free swinging movement, have the drawback of permitting disengagement while in an intermediate hinging condition. Fire dampers must be capable of assured operation under adverse conditions and hence improved features are constantly being developed in the hinging structure, the tracking structure and means to unfold the wall without detrimental binding, the latter area being particularly important in connection with horizontally disposed fire dampers. In addition, desired constructions for decreasing expense While still maintaining the requisite high reliability of operation are constantly being sought.

SUMMARY OF THE INVENTION Accordingly, a primary object of the invention resides in providing a novel folding Wall shutter assembly having plural sheet material strips with large and small interlocking hinge roll components on opposite longitudinal strip edges, the large and small hinge components on adjacent strips being slidably interlocked and both having a spiral roll form based on the same Archimedean spiral.

A further object, in conjunction with the preceding object, resides in the provision of a novel folding Wall shutter construction with a rectangular frame, a plurality of elongate thin sheet material strips With roll hinges on their elongate edges interengaged in interlocked relationship, support structure secured on the frame and pivotally supporting one edge roll of the end strips and mounting that end strip adjacent one end of and within the frame, guide tracks extending from one end of the frame along opposed frame sides to adjacent the other end of the frame, and projected hinge roll parts on the ends of the strips fit into and are guided by the guide tracks and are maintained within the frame as the folding strips are moved within the frame.

Another object in conjunction with the preceding object resides in providing that, in at least one of their limiting positions, the two opposing surfaces of interlocked spiral form roll hinges are substantially spaced apart a slight distance in a substantially parallel and confining relationship to a theoretical roll shape with a crosssection of an Archimedean spiral.

Still another object resides in providing a novel roll hinge construction between parallel edges of two pieces of sheet material which can be utilized as strips or blades in a folding wall, the roll edge on each piece being of spiral form and the two pieces being interengaged by sliding one spiral form roll edge into the other spiral form roll edge, the spiral form cross-section of the inner surface of one roll edge being substantially identical to the spiral cross-section of the outer surface of the other roll edge and both being developed closely adjacent a theoretical spiral roll, the cross-section of which is a mathematical Archimedean spiral.

A further object, in conjunction with the preceding object, resides in the provision of a novel roll hinge construction in a folding wall in which each strip has one type of spiral form hinge roll on one of its elongate edges and the other type of spiral form hinge roll edge on the other of its elongate edges. In connection with this object a still further object resides in providing a novel hinge construction in which the range between hinging limit positions can be varied by changing material thickness or desired clearance between hinge components at the hinging limit positions of the two interengaged spiral form, roll hinge edges, or changing the spiral formula constant a of the mathematical Archimedean spiral, or changing the hinge to channel angle of attachment. A still further object resides in providing a specific hinge construction in a folding Wall where the spiral form roll hinges start their spiral form at approximately 3/4 11' from the true spiral origin for the smaller hinge roll and at 1r/2 from the true spiral origin for the larger hinge roll and both spiral form rolls extend to slightly beyond 1r/2 from the origin enabling the range of hinging movement to be substantially 163.

A still further object, in conjunction with the preceding folding wall objects, resides in the novel provision of a sheet material strip, serving as a hinging fastener between the end strip of a folding wall and the inside of one end of the wall assembly frame, rigidly secured to the one end of the frame, extending between the side members of the frame and having a longitudinal edge with a roll hinge member adapted to be hingedly interengaged and interlocked with a roll hinge edge on one longitudinal edge of the end strip in the wall. In conjunction with this object, it is a further object to provide that the secured strip is at least a portion of one of the plurality of wall strips.

Still another object in conjunction with any of the foregoing folding wall objects resides in the provision of a novel flat strip coil torsion spring arrangement for closing the folding wall.

Further novel features and other objects of this invention will become apparent from the following detailed description, discussion and the appended claims taken in conjunction with the accompanying drawings showing a preferred structure and embodiment, in which:

FIGURE 1 is a top plan view of a horizontal folding Wall fire damper for use in a vertical flow path, constructed in accordance with the present invention;

FIGURE 2 is a transverse section taken on line 22 of the horizontal fire damper shown in FIGURE 1 as it would be installed in a duct sleeve, and also shows the bottom blade of the folding wall;

FIGURE 3 is a longitudinal section taken on line 3-3 of the horizontal fire damper shown in FIGURE 1 and shows the plurality of interlocked sheet metal blades spring urged and latched in a closed wall condition;

FIGURE 4 is a vertical section through a vertical fire damper having basic frame and wall components similar to those used in the construction of the FIGURE 1 horizontal damper, illustrating the blades maintained in their folded or open wall condition;

FIGURE 5 is a vertical section, similar to FIGURE 4, but illustrating the vertical fire damper after the fusible link melts and the blades are unfolded under gravity force, and also shows the preferred structure to pivotally secure the top blade to the frame;

FIGURES 6 and 7 are plan views of the two different blade fabrications as used in the disclosed folding wall construction;

FIGURES 8 and 9 are end views respectively of the blades illustrated in FIGURES 6 and 7 and show that the cross-section contours of both blades are identical;

FIGURE 10 is a greatly enlarged representation of the basic cross-section shape of the blade pieces;

FIGURES 11 and 12 are enlarged end views of the spiral form hinge portions formed along the two opposite edges of each blade and will be referred to in describing the formation of the hinge element configurations relative to an Archimedean spiral shown in FIGURE 11 and also in FIGURE 10.

FIGURE 13 is an enlarged end view of several interhinged blades, illustrating the disposition of the blades relative to each other when the wall is secured in its folded condition.

FIGURE 14 is an enlarged view showing the interengaged hinging portions of two adjacent blade when the wall is unfolded and the blades are hanging in a vertical wall disposition;

FIGURE 15 is a partial section showing a modified frame and track embodiment; and

FIGURE 16 is a plan view of a vertical disposed fire wall damper with a frame made like that shown in FIG- URE 15.

4 GENERAL The present invention was developed primarily for use as a folding wall fire damper and will be so described. Nevertheless, it is to be understood that similar folding blade wall construction can be used in other folding wall (or shutter) installations and will be considered within the confines of this invention.

The folding wall shutter or fire damper at it will be referred to throughout the remainder of this application is constructed of roll-formed interlocking steel strips, slats or blades somewhat similar in form and gage to sections of rolling fire doors which have been successfully used for more than years. Used as fire doors in openings in fire walls or as fire dampers in rectangular or round ducts, the folding wall members are assembled and maintained in a frame which can be mated with duct fittings or the frame can be constructed to serve as part of the duct work.

In the open position (see FIGURES 1 and 4) the blades 69 are folded in a zig-zag arrangement into a compact stack and are maintained in that condition by a fusible link 62. When the link is melted by excessive heat (see FIGURE 5), the interlocked blades unfold to form a steel curtain or wall that will seal the duct or other opening against passage of fire and will also serve as an effective barrier to the passage of smoke and toxic gases. In horizontal flow ducts the fire damper 2G is disposed vertically (see FIGURES 4 and 5) and its wall closes under gravity action, whereas in vertical flow ducts the dampers 22 are horizontally disposed (see FIGURES 1-3) and auxiliary power devices such as springs and 92, are used to close the wall.

Specific construction The fire damper assembly 24), shown in an open condition in FIGURE 4 and closed in FIGURE 5, is a basic assembly and as shown can be used as a vertically disposed fire damper in horizontal duct work or flow paths. Essentially the same basic assembly, modified by inclusion of additional structural components, is shown in FIGURES l, 2 and 3 for use as a horizontally disposed fire damper 22 in vertical ducts or fiow paths. Accordingly, details of the basic fire damper assembly which appear in both the horizontal flow damper and the vertical flow damper will be first described and then the additional components of the vertical fiow damper will be described.

The frame 24 is rectangular and, in one frame embodiment (FIGURES 1-5) is made from four sheet metal, formed pieces, a top channel shaped member 26, a bottom channel shaped member 28, and two side members 30 and 32 which include integrally formed guide channels 34 and 36, midportions 38 and 40 and extension flanges 42 and 44. The various bend formations in the side frame members provide stiffness which enables lighter gage metal to be used as well as providing the folding wall guide tracks 34, 36 and extension flanges 42, 44 by which the frame can be secured, as by screws (not shown) in a duct sleeve 46. The frame end, where the wall blades are stored when the Wall is folded, will be referred to as the top end whether the fire damper is vertically or horizontally disposed. This basic frame is substantially like the one shown in the aforedescribed co-pending application.

Alternatively, as shown in FIGURES l5 and- 16, the damper assembly 22 can be made with a duct shaped rectangular frame 5%) having fiat sheet metal Sides and ends and with blade guide tracks 52 made from sheet metal L strips or channel strips secured as by spot welding on the inside of the frame 60. The frame 5t} can be made from a single piece of sheet metal fastened as by welding at one corner joint 51 or from two pieces welded at opposite corner joints 51 and 53 or from three, four or more separate fiat pieces, suitably fastened to form the duct shaped frame.

In the embodiment of FIGURES 1-5 the two channel shaped top and bottom members 26 and 28 are placed over the ends of and embrace the side members 30 and 32 and are welded thereto to provide a rigid rectangular frame work, which serves to store the folding blades 60, and includes integral side channel guide tracks 34 and 36 to guide and maintain the blades in position during and after they are unfolded to a closed wall position within frame 24.

In the larger damper installations, one or more bracing rods 54, can be installed between the frame flange extensions 42 and 44 to provide extra strength and rigidity to the frame. The flanges 42 and 44 are apertured and countersunk at 56 to receive such a bracing rod 54, enabling the ends of rod 54 to be welded to the frame flange extensions without creating a weld-protuberance on the flat outer surface of the frame side members which, in installation, must normally fit within an adjoining duct 46, or round duct collar adapter, as desired. Similar countersunk apertures are preferably used to mount and enable welding of a top blade support rod 58 (FIGURES 3 and 4) to frame side members 30 and 32, described hereinafter.

The top channel shaped frame member 26 has more depth than the bottom frame member 28 and serves as a compartment within which the folded blades are, in effect, stored out of the duct flow path. For use in low velocity ducts the channel can be made shallower and for high velocity ducts the channel can be made slightly deeper than shown in FIGURE 1.

The folding wall blades are held in their folded condition by a fusible link 62 the apertured side of which are slipped over hook shaped ends 64 of link clips 66 and 68. Clips 66 and 68 are made from flat pieces of sheet metal, spot welded to the sides flanges of the top frame channel 26 or, as shown in FIGURE 16, clips 66' have a bent end 67 which is spot welded to the underside of the top flat piece of the duct type frame 50. These flat metal clips 66 and 68 have a somewhat springy characteristic and can be slightly pre-bent to spring away from the blade stack, when the fusible element melts, to positively remove the ends of the melted element 62 from possible interference with the blades 60 as they unfold.

The unique placement of the fusible link 63 disposes the link with substantial surface available to the flow path to thereby provide rapid response to duct air temperatures. This avoids the dangerous time-lag which will occur when a fusible link lays flat against masses of metal which act as heat sinks and will delay damper closing until the air temperature reaches a dangerously high value.

The topmost blade 600 (see FIGURES 3 and 4) is pivotally held adjacent the inner surface of top channel member 26 by a support rod 58 which extends through the free hinge roll along one edge of that blade 60a. The ends of rod 58 fit into countersunk apertures or notches at the top end of the side frame member channels 36 and are welded at such countersunk portions to the frame side members. Although not disclosed in detail, the welded connection of rods 58 (see in dotted lines in FIGURE 1) can be identical to that described and illustrated for the bracing rod 54 seen in FIGURE 1.

An alternate, and preferred, top blade pivotal mounting is depicted in FIGURE 5. Instead of a pivot support rod 58, a blade or strip 70, which can be identical to blades 60, is welded, e.g., spot or roll welding, to the inner surface of top channel member 26 with a roll hinge edge 72 disposed laterally across the frame 24 at the upper end of the channel guide tracks 34 and 36. A part 78 of the main body portion 76 of blade 70, adjacent its roll edge 72 is bent down sufficiently from the welded area to permit the topmost blade to freely slide into an interlocked freely hinging coaction with the welded blade piece 70. For convenience in standardization of blade parts the welded piece 70 can be a complete blade, but it is clearly apparent that only one roll edge 72 is required and the other one can be deleted if so desired. Use of the blade piece 70, secured as by welding to the top frame member, whether it be the channel type frame member 26 or a duct type frame (FIGURE 16), results in a substantially stronger structure for securing the top blade to the frame than is the pivot support rod 58 because the blade piece can be rigidly secured to the top frame member at a plurality of locations or continuously along its length whereas the pivot support rod 58 is secured only where its ends are welded to the frame.

Turning now to FIGURES 6 and 7, blades 60 are shown as being made with two different plan view configurations. The first configuration 60(1) has its projected end lugs 82 and 84 constituting portions of the large roll edge 74 projecting beyond the ends of the blade body 76(1); and the second configuration 60(2) has end lugs 83 and 85 constituting portions of the small roll edge 72 which are projected beyond the ends of the blade body 76(2). When blades 60 are assembled as a folding wall the two configurations 60(1) and 60(2) alternate, resulting in every second interlocked set of hinge rolls 72 and 74 being provided with matched end lugs 82, 83, and 84, 85 which in effect are projected tracking studs 86 and 88 (see FIGURE 1) fitting into the frame side channel guide tracks 34 and 36 and keeping the folding wall within frame 24 as and when the wall is folded and as and when it is unfolded. Note that the faces of alternate blades are reversed and hinging action of alternate interlocked hinges is opposite to provide the zigzag or accordian folding action.

In the vertically disposed fire damper 20, as shown in FIGURES 4 and 5, when the fusible link 62 melts, the folded blades 66 automatically drop and unfold into a closed wall damper condition shown in FIGURE 5. As illustrated the blades 60 unfold to an essentially planar wall with an excess blade 6% at the lowermost end provided for extra weight and to effect a better closure seal than is provided by a free hanging wall of blades which has a length equivalent to the frame length.

In the horizontally disposed fire damper, shown in FIG- URES 1, 2 and 3, the number of blades 60 is determined to provide a folding wall which at least matches the length of the damper frame. Being horizontal, the blades cannot automatically unfold as a result of gravity forces acting on the blades. Accordingly, a power means must be provided to unfold the blades when the fusible link 62 melts. A suitable power source is provided by using fiat coil springs, of the torsion type or the constant force type (trade marked NEGATOR). Two such coil springs 90 and 92 are used and mounted in a spring bracket 94, an auxiliary sheet metal channel fastened parallel to and along the bottom at the exterior of lower frame channel member 28. The spring coils 91 and 92 are located within the channel bracket on retaining rods or axles 96 which are secured in any convenient manner, e.g., by end swaging or welding at their ends, across the bracket channel 94 so the axes of the spring coils 91 and 93 are normal to the planar form of frame 24. The spring strips 90 and 92 pass from respective coils 91 and 93 through slotted apertures 98 (FIGURE 3) in the frame bottom member 28 immediately adjacent the blade guide tracks 34 and 36 extend to and fasten over the end lugs 83 and 85 of the lowermost blade 60. So mounted, the flat springs 90 and 92, are advantageously disposed particularly in their extended condition when the curtain is folded, wherein they are situated normal to the planar frame form, parallel to the air flow path through the duct and closely adjacent to the side frame members 30 and 32. Such disposition parallel to the air flow path will minimize duct flow loss and will avoid collecting of dirt, dust and other debris on the extended spring during the inactive damper condition, which in many installations will be over a period of years, perhaps the life of the installation.

The ends of both spring strips 90 and 92 are apertured I and are slipped over the respective projected hinge roll lugs 83 and 85 of the lowermost blade at the time the damper unit is assembled, thus providing a very simple spring end attachment to the folding wall. After assembly, the disposition of the blade end lugs 83 and 85 in guide tracks 34 and 36 will keep the ends of springs and 92 fastened over the blade end lugs. When the fusible link 62 melts, due to excess temperature, springs 90 and 92, whether of the flat coiled torsion type or of the NEGATOR type, will coil upon themselves and pull the folded blades to an unfolded or closed damper condition. The springs can be mounted ni the bottom frame member 28 so the fiat strips are parallel to the planar extent of the Wall but the flat spring can then collect dirt and debris which may be in the duct and such dirt and debris laying on the spring would be rolled up and may disrupt the spring force.

Shown in FIGURES l and 3 is a latching hook which extends through a suitable opening in the bottom frame channel 28 and is pivotally secured via a bracket 102 spot Welded to the underside of the frame channel 28. The nose edge 104 of the latch hook 100 is inclined from the end down to the hook portion providing a camming surface which faces the opposite end of frame 24. Upon release of the folded blades 60, springs 90 and 92 will rapidly pull the folded blades to the closed wall condition and as the bottom blade 60 approaches the bottom channel 28, its roll hinge edge 72 engages the inclined hook latch edge 102 and passes under and raises the latch hook 100 which then drops over the roll edge into latched engagement in a small opening 106 (see FIGURE 7) behind the roll edge 73 of the lowermost blade 6 3. The weight of latch hook 100 should normally be sufficient to cause the hook 100 to drop into hooked position but if desired a small coil wire torsion biasing spring 108 can be placed over the latch hook pivot and connected to bias the latch hook 100 into its latched position.

When larger dampers are utilized in a horizontal disposition, there may be a tendency for the long blades of a closed wall to sag in the center, particularly if subject to extensive heat. Accordingly, one or more fiat sag bars 110 can be secured as by welding to the side flanges of the top and bottom frame channels 26 and 28 on the side which is lowermost when the damper is horizontally disposed. If desired, bent flanges 112 (see FIGURE 3) at the ends of sag bar 110 can be used to weld the sag bar to the frame. When the wall is unfolded, the blades pass just above and do not engage the sag bar, however, should there be any heat sag in the blades they will engage the bar 110 which acts as a support and effectively prevents excess blade distortion. In actual installation, such a sag bar has held blade sag to a maximum of A3", even with blades made of 20 gage having a length of 40".

Blade shape An automatic fire damper with multiple interfitted hinged blades or slats requires a satisfactory shape for the longitudinal hinge sections on each side edge of the blade or slat. The shape on the edge of one blade must fit loosely into the adjoining hinge section of an adjacent blade in such a manner as to provide hinging action between adjacent blades sufficient to enable the blades to be folded against each other at one limit position and unfolded to a substantially planar Wall at the other limit condition. Furthermore, interlocking coaction between adjacent blades must be maintained throughout the entire operative and utilized arc of hinging. An arc of 180 is more than suflicient to enable accordian or zigzag folding and full planar wall shape unfolded condition but, as a practical matter, the necessary dimensions of the hinge rolls prevent the blades from folding to a condition much closer than a 15 divergence, hence the blade hinges need permit only an opening arc of hinging of about at which limit the blades will be disposed in an essentially planar wall shape.

As in the aforedescribed co-pending application, the cross-section shape for the hinge being used in this development, is based on a spiral curve. However, in this present invention, neither identical spirals nor mirror image spirals nor combined spiral-circular forms are used, rather the new shape is based on the two interfitted spiral form roll hinge sections lying on either side of and closely adjacent to a true spiral curve. The two spiral form hinge sections fit loosely enough to provide a clearance sufficient to allow for variations in metal thickness and manufacturing tolerance in forming the shapes.

The first phase in developing the shapes was the choice of a particular spiral curve to be used as a basis for forming the mating sections. The two spiral curves considered were (1) a spiral of Archimedes of the form and (2) the logarithmic spiral of the form log 1:126

where r is the distance from the origin to any point on the curve, a is a constant, and 0 is the angle of rotation of the radius vector in radians.

If a layout is made of these two mathematical curves using a value of in the first equation and person skilled in mechanics, hence are not shown. However, as the curves are extended beyond the logarithmic curve begins to diverge much more rapidly than does the Archimedes curve, in other words after the initial curve through 7/41.-, the Archimedes spiral is tighter than the logarithmic spiral. In hinge sections a rapidly diverging shape makes a thicker hinge joint and would be more likely to disengage at some stage of the hinging section diverging less rapidly, hence a shape following the spiral of Archimedes is desired.

The next item to be determined is the selection of a value for the constant a in the equation r=a9. The rapidity with which the spiral expands is dependent upon this value. The value assigned to a must be such that depending on the thickness of material used, there will be adequate clearance between two successive rotations of the radius vector to allow proper hinging action. The value of a for a commercially satisfactory folding wall blade, selected after successive trials, is:

The other critical problem is the choice of that section of the mathematical curve to be used in forming the hinge sections. The interrelated factors involved in this selection are:

(1) The thickness of material to be used.

(2) The desired overall width of hinge section.

(3) The amount of rotation desired in the hinging action.

(4) Desired clearance between the interfitted hinge sections.

In an exemplary fire wall, applicants have used ma terial 0.040" thick. Based on a desired total outside dimension of the hinge section not to exceed 0.500", an Archimedean spiral curve A (FIGURE 11) was generated with the constant Referring to FIGURE 11, laying the two interfitting shapes 120 and 122'on either side of the mathematical curve A, successive trials determined the optimum inside starting point for the two sections to be 3/41r for the smaller (or inside) hinge section 122 and 7r/2 for the larger (or outside) hinge section 120. This position of the hinge sections is with the blades in their folded wall position.

The two hinge sections 120 and 122 follow the Archimedean spiral curve to a point a little past 57/2 radians from the origin, at which point the hinge section 120, 122 desirably become tangent to short flanged edges on the main body of a blade. The main part of a blade 60 (as shown in FIGURE 10) is channel shaped with a flat main body 76 and longitudinal substantially normal edge flanges 124 and 126. In FIGURE 10, line BB represents the location where the spiral hinge section 120 becomes tangent to blade edge flange 124 and line C-C represents the location where section 122 becomes tangent to blade edge flange 126.

Both hinge sections 120 and 122, as just described, are continuous spiral curve forms, both of which parallel the same mathematical spiral curve.

The inside (or smaller) hinge section 122 starts later on the basic spiral curve and follows the spiral curve a little farther along the curve than does the larger (or outside) hinge section 120. This is intended to be accurately depicted in FIGURE 11, and is due to the fact that when the adjacent blades 60 of the damper fire Wall are in the folded position, as in FIGURE 13, the main body portions 76 (depicted as fiat although they could be made wavy or zigzag) of the channel of two adjacent blades are not parallel but if extended to intersect will form an angle of approximately 17 (see FIGURE 13). Therefore, the curve of the smaller (or inside) section 122 follows the spiral curve A 17 further than does the larger section 129. Furthermore, due to this 17 angle between two adjacent blades 60 in the folded position, it follows that for the fiat main body portions 76 of adjacent blades to be parallel, i.e., the wall to be planar when they are unfolded, the hinging action between the two blades only needs to have a range of 163. Blades constructed in accord with the exemplary description are intended to hinge through at least a 163 range but, because of the design clearance between the nested spiral forms, will actually hinge within several degrees of a 180 range.

Using the two interfitting hinge sections 120 and 122 which have been defined, and with reference now to FIG- URE 12, it is found that when the smaller (inside) shape 122 is rotated 163, using the origin of the previously defined spiral curve as the theoretical axis of rotation, the smaller section will now lie outside the larger curve with their two adjacent surfaces approximately parallel. It can be shown mathematically that with the two hinge sections formed as defined above and with 0.014 clearance in the folded position, then, when rotated 163 to the open position, as described above, the two sections will again be in a position to have a substantially uniform 0.014" clearance in this open position.

Equation of Archimedean spiral:

r=zz where:

r=distance from origin to any point on curve a=constant (length of r/radian) 6=angular rotation from origin (measured in radians) In FIGURE 11, line A is the mathematical Archimedean spiral and sections 120 and 122 are the two hinge sections lying on either side of the spiral A.

1 0 b=clearance from curve A to either adjacent hinge section and 122. 2b=total clearance between hinge sections c=thickness of sheet material used in the hinge sections 21:00 (b-I-c) "2= When the two sections are rotated relative to each other, let the angle of rotation=.

Turning to FIGURE 12, the desired condition is:

The same origin of the spiral Archimedean curve is used in the two positions of FIGURES 11 and 12, the larger section 120 remaining in the same position, and the smaller section 122 in FIGURE 12 having been rotated using the origin of spiral curve A as its center of rotation.

Thus the maintenance of a constant clearance 212 between the surfaces at the limit positions, as shown in FIGURES 11 and 12 is independent of 0, or the location of any given point on the curve, but is dependent upon the angle of relative rotation 5, the thickness of material C in the hinge sections, and the constant a.

In determining how to shape the desired spiral hinge forms, the angle at will be the hinging angle through which it is desired to rotate the blades in order to have the appropriate adjacent strip disposition in both open and closed positions, as required for a specific installation.

If one chooses a desired blade cross-section to meet certain factors, i.e., the width of each blade can be chosen as approximately 1.80", the maximum hinge roll dimension held to 0.500" and metal thickness of 0.040 then the desired range of hinging of 163 between folded and full open limits can be experimentally determined by relatively accurate measurements.

-17=2.845 rads.= c=0.040" (20 gage) (desired constant determined from large scale models 27rd 41) 2c then b 21ra a0-2c Substituting the above values:

The total clearance between sections equals 2b=0.0l4". Therefore the hinge section shapes 120 and 122 can be formed with appropriate clearance from mathematical spiral to obtain a desired hinging action.

It will be noted that with the hinge shapes as theoretically described with respect to FIGURES 11 and 12, the rotation between the two sections 120 and 122 was assumed about a fixed axis, namely the origin of the spiral curve. In actual practice the hinge sections can be shifted a considerable amount away from rotation about the origin of the Archimedean spiral at all intermediate hinging angles. However, at locations which approximate both limit positions of folded and unfolded blades, the spiral basis about which both hinge elements were shaped will have essentially the same point of origin or, considering the hinge roll as having length, the same axis. In the folded condition the interlocked hinge rolls 72 and 74 will be substantially coextensive and will have the calculated clearance between adjacent surfaces and thus have a loose fit. When swung or unfolded through approximately 163, again they will have the calculated clearance between adjacent surfaces and thus have a loose fit. Because of such clearance between adjacent surfaces, the permitted hinging action goes about 17 beyond the 163 range until the adjacent surfaces actually engage and prevent further hinging.

Using present day production facilities and considering the close tolerance of the desired shapes the small spiral roll element 72 resulting from the exemplary calculations is about as small as can be accurately rolled on 20 gage metal, without following a multiplicity of complex rolling steps (a costly operation). Available production facilities are capable of closely approximating the desired spiral-like curves with a minimum of rehandling. HOW- ever, because. the inside terminal portions of the strips, marked (a) in FIGURE 11, are so near the actual edge of the raw strip material, the desired terminal curve cannot quite be readily obtained with mass production tools. This causes a condition in the hinge rolls which deviates slightly from but is substantially parallel to the desired Archimedes spiral. In some instances this deviation could cause the two raw edges of the two shapes 72 and 74 to engage and bind at an intermediate hinging angle, but the problem can be avoided simply by rounding the cut edges (x), see FIGURE 11, of the raw strip stock before it is rolled into the blade shape. Another expedient, which can be used to successfully overcome the possibility of binding Of the terminal edges, is to slightly change the joinder flange 126 for the small roll hinge 72, making its angle approximately 85 relative to body portion 76 rather than 90. Such modifications overcome mechanical problems arising from mass production forming of the desired spiral forrn shapes. The precise desired shapes can be rolled and formed by hand if desired, although that procedure would not be economically feasible.

The blade is, in effect, a shallow channel with the tWO spiral like curves 128 and 122, each of which is tangent to an associated flange of the channel. When the smaller rolled hinge edge 72 of one blade 60 is interlocked with the large rolled hinge edge 74 of an adjacent blade 60, two wall sections are interlocked and will freely rotate approximately 180 from an essentially folded disposition (17 divergence) without becoming disengaged at any angle within the limits of rotation. The free operation of these shapes is dependent upon a substantially accurate forming of the respective spiral form curves. The

mass production blades, as described hereinbefore, operate extremely well, rotate smoothly through approximately 180 and will not become disengaged nor will they bind at any point within the desired limits of hinging action.

Throughout this specification, securing of the various damper components into a unit assembly has been described as accomplished by welding primarily because welded joints are highly reliable and desirable for obvious reasons in construction of a fire damper. However, the securing means could be other well known fastening devices such as screws or nuts and bolts, and if the folding wall were to be used for other purposes, the material could be sheet plastic instead of sheet metal.

The invention may be embodied in other specific forms without departing from the spirit of essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative. and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A folding wall assembly comprising: a plurality of adjacent, parallel elongate sheet material strips, each of the two elongate edges of said strips including a spiral form roll hinge means, each set of adjacent parallel edges of each adjacent pair of strips comprising: two interengaged, interlocked said roll hinge means of different size. the spiral form cross-section of the inner surface of the larger sized one of said two interengaged roll hinge means being substantially identical to the spiral form cross-section of the outer surface of the smaller sized one of said interengaged roll hinge means and developed to lay substantially along a theoretical spiral which is a mathematical Archimedean spiral; said spiral form roll hinge means start their spiral form at approximately 3/411- radians from the point of origin for said Archimedean spiral for the smaller size hinge means and at 1r/2 radians from said point of origin for the larger size hinge means; both spiral form roll hinge means extend to slightly beyond 5102 radians from said point of origin; the range of hinging movement is substantially at least 163 between two limit positions each of which positions is determined by binding engagement between interlocked spiral form roll hinge means; and said spiral form roll hinge means remain interlocked throughout the range of hinging movement between said two limit positions.

2. A folding Wall construction comprising: a rectangular frame means; a plurality of elongate thin sheet material strips with hinging means on their elongate edges; hinging means on adjacent strips being interengaged in interlocked relationship throughout the hinging movement permitted between adjacent strips; means located adjacent one end of said frame means and rigidly secured on said frame means, pivotally engaged by an elongate. portion of one edge hinging means of an end one of said plurality of strips and securing said end strip adjacent one end of and within said frame means; guide track means in said frame means extending from said one end of said frame means along opposed sides of said frame means to a position adjacent the end of said frame means opposite its said one end; means on the ends of said strips adapted to engage and be guided by said guide tracks means as said strips are moved within said frame; said hinging means comprising adjacent lengths of roll formed sheet material edges of said strips, each length having a spiral form cross-section and one rolled length having a smaller spiral form than the other rolled length, slidable lengthwise into interlocked hinging engagement with said other roll length and capable of hinging action between two selflimiting positions, the two adjacent faces of said two rolled spiral lengths when said two interengaged rolled lengths are in one of said self-limiting positions being substantially equidistant apart and confining a theoretical roll shape with a cross-section of an Archimedean spiral. and the larger spiral form having its spiral shape starting closer to the point of origin of the Archimedean spiral than does the smaller spiral form.

3. folding wall construction as defined in claim I. wherein said pivotal hinging means secured to said frame means comprises a rod having its ends rigidly secured in the s des of said frame means closely adjacent one end of said frame means and projecting with suflicient clearance through one of said roll formed edges of said end one of said strips to permit said end one of said strips to freely ivot on said rod.

4. A folding sheet metal Wall construction as defined in claim 3, said wall being intended for use within a confining sleeve and the outer surface of said frame means haying a surface adapted to closely fit within the confining sleeve; said sides of said frame means being coaxially apertured to receive the ends of said rod; the portions of said frame means adjacent said apertures being countersunk toward the inner confines of said frame means, said rod being made of metal and having a length substantially equal to the exterior width of the frame means and extending between and welded to said countersunk portions.

5. A folding wall construction comprising: a rectangular frame means; a plurality of elongate thin sheet material strips with hinging means on their elongate edges; hinging means on adjacent strips being interengaged in interlocked relationhsip throughout the hinging movement permitted between adjacent strips; means secured on said frame means, pivotally engaging one edge hinging means of an end one of said plurality of strips and securing said end strip adjacent one end of and within said frame means; guide track means in said frame means extending from said one end of said frame means along opposed sides of said frame means to a position adjacent the end of said frame means opposite its said one end; means on the ends of said strips adapted to engage and be guided by said guide tracks means as said strips are moved within said frame; said strip guide means being longitudinal lug portions comprising an extension of said roll formed sheet material from at least one longitudinal roll hinge edge of each strip; said hinging means comprising adjacent lengths of roll formed sheet material edges of said strips, each length having a spiral form cross-section and one rolled length having a smaller spiral form than the other rolled length, slidable lengthwise into interlocked hinging engagement with said other roll length and capable of hinging action between two self limiting positions, the two adjacent faces of said two rolled spiral lengths when said two interengaged rolled lengths are in one of said self limiting positions being substantially equidistant apart and confining a theroretical roll shape with a cross-section of an Archimedean spiral; and flat strip coil spring means, carried on the other end of said frame means, including spring end anchor means connected to said lug portions of the other end one of said strips and thereby exerting a biasing force on said strips urging said hinged strips from folded condition to an unfolded condition.

6. A folding wall construction comprising: a rectangular frame means; a plurality of elongate thin sheet material strips with hinging means on their elongate edges; hinging means on adjacent Strips being interengaged in interlocked relationship throughout the hinging movement permitted between adjacent strips; means secured on said frame means, pivotally engaging one edge hinging means of an end one of said plurality of strips and securing said end strip adjacent one end of and within said frame means; guide track means in said frame means extending from said one end of said frame means along opposed sides of said frame means to a position adjacent the end of said frame means opposite its said one end; means on the ends of said strips adapted to engage and be guided by said guide tracks means as said strips are moved within said frame; said hinging means comprising adjacent lengths of roll formed sheet material edges of said strips, each length having a spiral form cross-section and one rolled length having a smaller spiral form than the other rolled length, slidable lengthwise into interlocked hinging engagement with said other roll length and capable of hinging action between two self limiting positions, the two adjacent faces of said two rolled spiral lengths when said two interengaged rolled lengths are in one of said self limiting positions being substantially equidistant apart and confining a theoretical roll shape with a cross-section of an Archimedean spiral; said secured hinging means comprising a sheet material strip rigidly secured to the inside of said one end of said frame means, extending substantially between the sides of said frame means, and having a longitudinal edge with a said roll formed hinge means adapted to be hingedly interengaged and interlocked with a roll formed hinge means on one longitudinal edge of said one end strip.

7. A folding metal wall construction as defined in claim 6, wherein said secured strip is welded to the said end of said frame means.

8. A folding wall construction as defined in claim 6, wherein said secured strip is at least a portion of a strip similar to one of said plurality of strips.

9. A folding wall construction comprising: a rectangular frame means, a plurality of elongate thin sheet material strips with hinging means on their elongate edges, hinging means on adjacent strips being interengaged in interlocked relationship throughout the hinging movement permitted between adjacent strips; means secured on said frame means, pivotally engaging one edge hinging means of an end one of said plurality of strips and securing said end strip adjacent one end of and within said frame means comprising a sheet material strip rigidly secured to the inside of said one end of said frame means, extending substantially between the sides of said frame means, and having a longitudinal edge with a said roll formed hinge means adapted to be hingedly interengaged and interlocked with a roll formed hinge means on one longitudinal edge of said one end strip; guide track means in said frame means extending from said one end of said frame means along opposed sides of said frame means to a position adjacent the end of said frame means opposite its said one end; means on the ends of said strips adapted to engage and be guided by said guide track means comprising adjacent lengths of roll formed sheet material edges of said strips; one roll form edge having a smaller roll form than the other roll formed edge and slidable lengthwise into interlocked hinging engagement with said other roll length and enabling hinging action between two self limiting positions.

10. A folding metal wall construction as defined in claim 9, wherein said secured strip is welded to the said end of said frame means.

11. A folding wall construction as defined in claim 9, wherein said secured strip is at least a portion of a strip similar to one of said plurality of strips.

12. A folding wall construction as defined in claim 9, wherein said secured strip is bent so that its edge portion which includes the roll formed hinge means is spaced away from the said one end of said frame means.

References Cited UNITED STATES PATENTS 790,632 5/1905 Hall -1 1,205,707 11/191'6 Cahill 160-235 X 1,987,774 1/1935 Hall l6l78 X 2,093,054 9/1937 Negrini 160--235 2,586,561 2/1952 Poggi 160-235 X 3,242,523 3/1966 Daley 16-171 3,273,632 9/1966 McCabe 160-1 PETER M. CAUN, Primary Examiner US. Cl. X.'R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 Dated DECEMBER 23 1959 Inventor(s) L. BOWMAN TURNER AND WILLIAM M. HARMON It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 12, "hi" should be -in--.

Column 9, line 17, "section 120, 122" should be -sections 120,122-

Column 12, line 64, "1" should be --2--.

SIGNEE Au SEALED MT 6 m (SEAL) I: Am:

Edward M. 1 10101181. Ir. mm B. m.

Atflcsting Officer commissioner of Iatenta 

